diff --git a/src/device/isapnp.c b/src/device/isapnp.c
index 341a9ff7e..08290e10b 100644
--- a/src/device/isapnp.c
+++ b/src/device/isapnp.c
@@ -221,6 +221,11 @@ isapnp_read_data(uint16_t addr, void *priv)
 	case 0x04: /* Resource Data */
 		CHECK_CURRENT_CARD();
 
+		/* The break; inside CHECK_CURRENT_CARD(); only breaks out of the do { ... } while (0);
+		   so make sure to break again here. */
+		if (!card)
+			break;
+
 		isapnp_log("ISAPnP: Read resource data index %02X (%02X) from CSN %02X\n", card->rom_pos, card->rom[card->rom_pos], card->csn);
 		if (card->rom_pos >= card->rom_size)
 			ret = 0xff;
@@ -233,6 +238,11 @@ isapnp_read_data(uint16_t addr, void *priv)
 		ret = 0x00;
 		CHECK_CURRENT_CARD();
 
+		/* The break; inside CHECK_CURRENT_CARD(); only breaks out of the do { ... } while (0);
+		   so make sure to break again here. */
+		if (!card)
+			break;
+
 		isapnp_log("ISAPnP: Query status for CSN %02X\n", card->csn);
 		ret = 0x01;
 
@@ -242,6 +252,11 @@ isapnp_read_data(uint16_t addr, void *priv)
 		ret = 0x00;
 		CHECK_CURRENT_CARD();
 
+		/* The break; inside CHECK_CURRENT_CARD(); only breaks out of the do { ... } while (0);
+		   so make sure to break again here. */
+		if (!card)
+			break;
+
 		isapnp_log("ISAPnP: Query CSN %02X\n", card->csn);
 		ret = card->csn;
 
@@ -261,7 +276,14 @@ isapnp_read_data(uint16_t addr, void *priv)
 	case 0x28: case 0x29: case 0x2a: case 0x2b:
 	case 0x2c: case 0x2d: case 0x2e: case 0x2f:
 		CHECK_CURRENT_CARD();
+
+		/* The break; inside CHECK_CURRENT_CARD(); only breaks out of the do { ... } while (0);
+		   so make sure to break again here. */
+		if (!card)
+			break;
+
 		isapnp_log("ISAPnP: Read vendor-defined register %02X from CSN %02X\n", dev->reg, card->csn);
+
 		if (card->read_vendor_reg)
 			ret = card->read_vendor_reg(0, dev->reg, card->priv);
 		break;
@@ -432,6 +454,11 @@ isapnp_write_data(uint16_t addr, uint8_t val, void *priv)
 	case 0x07: /* Logical Device Number */
 		CHECK_CURRENT_CARD();
 
+		/* The break; inside CHECK_CURRENT_CARD(); only breaks out of the do { ... } while (0);
+		   so make sure to break again here. */
+		if (!card)
+			break;
+
 		ld = card->first_ld;
 		while (ld) {
 			if (ld->number == val) {
@@ -498,7 +525,14 @@ isapnp_write_data(uint16_t addr, uint8_t val, void *priv)
 	case 0x28: case 0x29: case 0x2a: case 0x2b:
 	case 0x2c: case 0x2d: case 0x2e: case 0x2f:
 		CHECK_CURRENT_CARD();
+
+		/* The break; inside CHECK_CURRENT_CARD(); only breaks out of the do { ... } while (0);
+		   so make sure to break again here. */
+		if (!card)
+			break;
+
 		isapnp_log("ISAPnP: Write %02X to vendor-defined register %02X on CSN %02X\n", val, dev->reg, card->csn);
+
 		if (card->write_vendor_reg)
 			card->write_vendor_reg(0, dev->reg, val, card->priv);
 		break;
diff --git a/src/scsi/scsi_aha154x.c b/src/scsi/scsi_aha154x.c
index e374de25e..8e4bf93be 100644
--- a/src/scsi/scsi_aha154x.c
+++ b/src/scsi/scsi_aha154x.c
@@ -193,7 +193,7 @@ aha154x_eeprom(x54x_t *dev, uint8_t cmd,uint8_t arg,uint8_t len,uint8_t off,uint
 	if (dev->type == AHA_154xCF) {
 		if (dev->fdc_address > 0) {
 			fdc_remove(dev->fdc);
-			fdc_set_base(dev->fdc, dev->fdc_address);
+			fdc_set_base(dev->fdc, (dev->nvr[0] & EE0_ALTFLOP) ? 0x370 : 0x3f0);
 		}
 	}
     }
@@ -745,6 +745,13 @@ aha_setnvr(x54x_t *dev)
 	f = NULL;
     } else
 	aha_initnvr(dev);
+
+    if (dev->type == AHA_154xCF) {
+	if (dev->fdc_address > 0) {
+		fdc_remove(dev->fdc);
+		fdc_set_base(dev->fdc, (dev->nvr[0] & EE0_ALTFLOP) ? 0x370 : 0x3f0);
+	}
+    }
 }